Summary/Overview of Instrument: The first part of Trail Making Test (TMT) test, TMT-A, requires the subject to rapidly sequence numbers from 1 through 25, with the score being the time to complete the task. The second part, TMT-B, is a more difficult cognitive flexibility task requiring the subject to follow a sequential pattern while shifting cognitive sets, sequencing from 1 to 13 while switching between numbers and letters (i.e., 1-A-2-B-3-C,…), with the score being the time to complete the task. The utility and psychometric properties of the Trails B are so well accepted that it is one of the few measures that it is used across neurologic and psychiatric clinical and research patient populations.

Construct measured: Psychomotor speed and executive functions

Generic vs. disease specific: Generic

Intended use of instrument/purpose of tool: The Trail Making Test is a measure of psychomotor speed, visual scanning, and executive ability.

Scoring: Scoring of A and B are reported as the number of seconds required to complete the task. Higher scores indicate greater impairment. Performance varies by age and education, and thus normative standards are used to classify patient performance. Errors affect the patient’s score only in that the correction of errors is included in the completion time for the task. If a patient has not completed both parts after five minutes, it is unnecessary to continue the test. In addition to the direct scores, the B-A difference score, the B:A ration, and the B-A/A proportional score have also been used as indicators of certain cognitive operations or specific markers of brain damage (Sanchez- Cubillo et al., 2009). Note: Parts A & B must be completed together and in the correct order for test administration to be valid.

Standardization of scores to a reference population: Raw scores (time to complete) are converted to scaled scores (0–19). Scale score is converted to t score by sex, education, age, and ethnicity. Norms are from the Halstead-Reitan Battery (Heaton et al., 2004).

The HD-CAB is a cognitive battery designed specifically for use in late premanifest and early HD clinical trials. This six test assessment battery which includes the Trail Making B test was found be sensitive to disease status and reliable in an observational study in 105 control, 103 premanifest-HD, and 55 early HD subjects (Stout et al., 2014).

Construct validity: Subtests correlate with visual search tasks (Ehrenstein et al., 1982). In a study by Sanchez-Cubillo and colleagues (2009) suggested that the TMT-A mainly requires visuoperceptual abilities, while the TMT-B requires “primarily working member and secondarily task-switching ability”.

Sensitivity to Change/Ability to Detect Change (over time or in response to an intervention): In published cross-sectional (Stout et al., 2011) and internal analyses (PREDICT-HD), Parts A and B are sensitive to impairments in premanifest HD, especially Part B in individuals who are closer to an expected diagnosis. Unpublished internal analyses of 7-year longitudinal data (PREDICT) show differences in rates of longitudinal change in premanifest HD on both subtests, but especially Part A, compared to gene negatives.

Cross sectionally, the TRACK-HD study found that healthy controls performed significantly better than both the early HD and the premanifest HD groups. Longitudinally, the TRACK-HD study found significant differences in rates of change for early HD compared to controls, but did not find significant differences in rates of change for premanifest HD compared to controls.

The TRACK-HD premanifest participants may be less likely to show cognitive effects than the PREDICT-HD Premanifest participants because 1) they are further from estimated onset based on CAG repeat length and age (Langbehn et al., 2004) and 2) they are potentially less progressed in actuality because the TRACK-HD study excluded premanifest subjects based on UHDRS motor scores >= 5. Generally speaking, cognitive tests will be more effective metrics in studies of premanifest HD when the focus is on subjects that are close to onset.

Strengths: Parts A and B are sensitive in cross-sectional and longitudinal studies of prodromal HD. Task has been tested at sites in the United States, Canada, United Kingdom, Australia, Germany, and Spain.

Weaknesses: The examiner must carefully monitor a participant’s performance to accurately score errors. The reliability of test administration can vary by examiner’s reaction time in noticing errors and pointing them out, which introduces imprecision. More severe motor impairment may influence results. Participants who are very cognitively impaired may not be able to complete the task, which must be dealt with statistically (e.g., set a maximum time for noncompleters).

Availability: In the Public domain, May be photocopied, though there are versions available for purchase.

Special Requirements for administration: Stopwatch.

Administration Time: 10 minutes.

References

ReitanRM. Validity of the Trail Making test as an indicator of organic brain damage. Percept Mot Skills. 1958;8:271–276.